POJ 3461 kmp

Oulipo

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 40168		Accepted: 16135

Description

The French author Georges Perec (1936–1982) once wrote a book, La disparition, without the letter 'e'. He was a member of the Oulipo group. A quote from the book:

Tout avait Pair normal, mais tout s’affirmait faux. Tout avait Fair normal, d’abord, puis surgissait l’inhumain, l’affolant. Il aurait voulu savoir où s’articulait l’association qui l’unissait au roman : stir son tapis, assaillant à tout instant son imagination, l’intuition d’un tabou, la vision d’un mal obscur, d’un quoi vacant, d’un non-dit : la vision, l’avision d’un oubli commandant tout, où s’abolissait la raison : tout avait l’air normal mais…

Perec would probably have scored high (or rather, low) in the following contest. People are asked to write a perhaps even meaningful text on some subject with as few occurrences of a given “word” as possible. Our task is to provide the jury with a program that counts these occurrences, in order to obtain a ranking of the competitors. These competitors often write very long texts with nonsense meaning; a sequence of 500,000 consecutive 'T's is not unusual. And they never use spaces.

So we want to quickly find out how often a word, i.e., a given string, occurs in a text. More formally: given the alphabet {'A', 'B', 'C', …, 'Z'} and two finite strings over that alphabet, a word W and a text T, count the number of occurrences of W in T. All the consecutive characters of W must exactly match consecutive characters of T. Occurrences may overlap.

Input

The first line of the input file contains a single number: the number of test cases to follow. Each test case has the following format:

• One line with the word W, a string over {'A', 'B', 'C', …, 'Z'}, with 1 ≤ |W| ≤ 10,000 (here |W| denotes the length of the string W).
• One line with the text T, a string over {'A', 'B', 'C', …, 'Z'}, with |W| ≤ |T| ≤ 1,000,000.

Output

For every test case in the input file, the output should contain a single number, on a single line: the number of occurrences of the word W in the text T.

Sample Input

3
BAPC
BAPC
AZA
AZAZAZA
VERDI
AVERDXIVYERDIAN

Sample Output

1
3
0

Source

BAPC 2006 Qualification

 

莫名其妙TLE

 #include<iostream>
 #include<cstdio>
 #include<cstring>
 using namespace std;
 char a[];
 char b[];
 int  p[];
 int la,lb;
 int j;
 int ans;
 inline void makep()
 {

     j=;
     for(int i=;i<la;i++)
     {
         while(j>&&a[i]!=a[j])
         j=p[j];
         if(a[i]==a[j])
         j++;
         p[i]=j;
     }
     return ;
 }
 inline void KMP()
 {
     j=;
     ans=;
     for(int i=;i<lb;i++)
     {
         while(b[i]!=a[j]&&j>)
         j=p[j-];
         if(b[i]==a[j])
         j++;
         if(j==la)
         {
             ans++;
             j=p[j-];
         }

     }
     printf("%d\n",ans);
     return ;
 }

 int main()
 {
     int n;
     scanf("%d",&n);

     for(int i=;i<=n;i++)
     {
         memset(p,,sizeof(p));
         scanf("%s%s",a,b);
         la=strlen(a);lb=strlen(b);
         makep();
         KMP();
     }

     return ;
 }

TLE

AC

 #include<cstdio>
 #include<cstdlib>
 #include<cstring>
 #include<iostream>
 using namespace std;

 int n,la,lb;
 int next[];
 char a[],b[];

 void getnext()
 {
     int j=-;
     next[]=-;
     for(int i=;i<lb;i++)
     {
         if(j!=- && b[j+]!=b[i])    j=next[j];
         if(b[j+]==b[i])    j++;
         next[i]=j;
     }
 }

 int kmp()
 {
     int ans=;
     int j=-;
     for(int i=;i<la;i++)
     {
         if(j!=- && a[i]!=b[j+])    j=next[j];
         if(b[j+]==a[i])    j++;
         if(j==lb-)
         {
             ans++;
             j=next[j];
         }
     }
     return ans;
 }

 int main()
 {
     scanf("%d",&n);
     for(int u=;u<=n;u++)
     {
         scanf("%s %s",b,a);
         la=strlen(a);
         lb=strlen(b);
         getnext();
         printf("%d\n",kmp());
     }
 }

AC